Neurofeedback (EEG biofeedback) is increasingly advocated for treatment of attention-deficit/hyperactivity disorder (ADHD) despite a thin evidence base. The numerous open and partially controlled studies suffer serious design flaws, especially lack of blinding and rare randomization. In particular, there is no published double-blind randomized clinical trial (RCT). The primary aim of this R34 pilot application is to prepare for such a RCT by resolving several feasibility/efficiency/palatability issues that would determine appropriate design. These include the frequency and number of treatments and feasibility of blinding with new technology. Secondary aims include to replicate, with an improved blinding technique, the effect sizes (d>0.7) found in prior studies and to explore age, sex, and ADHD subtype effects. Thirty-six boys and girls aged 6-12 with rigorously diagnosed DSM-IV ADHD not currently taking medication will be twice-randomized: first to active neurofeedback (n=24) vs. sham neurofeedback (n=12), and simultaneously to 2 vs. 3 times a week treatment frequency (18 in each frequency, 12 active and 6 sham) for 40 treatments. At treatment 24, major assessments will include measures of satisfaction and blinding, and subjects will be given the option of switching to the opposite treatment frequency for the remaining 16 treatments to generate a practical measure of schedule palatability. Major assessments (at baseline, treatment 12, treatment 24, treatment 40, and follow-up) will include measures of symptoms, functional impairment, academic performance/achievement, and neuropsychological tests of attention, vigilance, and executive functioning. Every 3 treatments parents will rate ADHD symptoms and every 6 treatments teachers will rate, to track the response curve over time. Baseline EEG arousal and ADHD subtype will be examined as possible moderators. By determining the optimal frequency and number of treatments and demonstrating feasibility of double blinding, this pilot study should pave the way for a definitive large RCT of neurofeedback. Attention-deficit/hyperactivity disorder (ADHD) is the most common child mental disorder, with significant impact on academic, social/marital, and occupational function, and even on safety. Because current established treatments are less than optimal for almost half of patients and many decline the most effective ones (stimulant medication), there is a large public health need for additional treatment options such as neurofeedback (EEG biofeedback), which has encouraging preliminary open and partially controlled studies but no published double-blind studies. Because of its expense and laborious intensity, rigorous testing is needed, and this application is in response to that need, proposing a pilot study to resolve some feasibility and design issues preparatory to a large double-blind randomized trial.